1. Field of the Invention
The present invention relates generally to High Definition Multimedia Interface (HDMI), and more specifically to Consumer Electronics Control (CEC).
2. Discussion of the Related Art
The High Definition Multimedia Interface (HDMI) is an all digital audio/video interface which has become a modern replacement for previous standards such as Video Graphics Array (VGA), Separate Video (S-Video), composite video, and Digital Visual Interface (DVI). HDMI allows a variety of electronics to be linked together as a network to create a home theater system for a user. These electronics may be devices such as a DVD player, television, audio/video receiver, or a video game console. The HDMI standard utilizes a Consumer Electronics Control (CEC) protocol to provide high-level control functions between devices in an HDMI network. The CEC protocol was first utilized to pass remote control data between television sets and attached devices, such as DVD players. For an HDMI network consisting of a television and DVD player, utilizing CEC, the user could insert a DVD into the DVD player and it would start playing as well as turn the TV on and switch to the DVD input.
The CEC protocol is based on the European AV link protocol and communicates data on a single wire bi-directional bus known as the CEC line. The transfer rate chosen for the CEC line in an HDMI network has been calculated to account for a fully populated network. As such, a standard transfer rate of about 400 bits/sec was selected to take into account the multiple collisions, interferences, and repeaters which occur in an HDMI network. A single transfer rate of 400 bps was selected in order to create compatibility between the various devices in an HDMI network for exchanging messages as prescribed in detain in “HDMI Specification 1.0, Supplement 1: Consumer Electronics Control (CEC).” If a user were to transfer information other than what is outlined in the HDMI specification, a secondary bus would need to be implemented to carry the additional information.